The proposed study will assess the cost-effectiveness of mixed mode methods for collecting health data by combining diary mail-in procedures, which yield higher quality data, with telephone interviews, which are less expensive. The objective of the research is to determine how the cost of diary panel procedures could be reduced without unduly compromising the quality of the data obtained. The design calls for three rotating panels of 400 households each. At the conclusion of an initial interview, each respondent will be asked to maintain a monthly or bimonthly diary of household health events for a four-month period. Any respondent who fails to return a monthly diary will be interviewed by telephone. One year later each household will be asked to continue in the panel for a period of one, two, or four months. The following experimental treatments will be tested utilizing a 2 to the second power x 3 x 4 factorial design: 1) initial face-to-face vs. telephone interviews; 2) compensation for a completed diary or telephone interview vs. compensation contingent on completion of a diary; 4) one-month diary forms vs. two-month diary forms; 5) telephone vs. monthly mail vs. no scheduled contact with households.